Looking for a greenhouse that can be covered to force flowering?

Question:need to darken for 12 hr period

Answers:
I use 75 gallon fish tanks for most of my stuff,build one out of Plexi just for the purpose so that you can wrap or move to a darker spot.The tanks I use is like Hawii covered in glass I can force flowering or grow 12" tomatoes in 22 day's from seed.avg 80 deg. with tons of humidity in all organic compost.( for tomatoes)